There is currently a worldwide demand for a natural and health-oriented non-artificial seasoning with no use of additives, as led by Japan and developed countries including European countries and the U.S. Regarding this demand, although a high-value added extract with enhanced “umami” such as nucleic acid has been developed in the yeast extract industry, development is also progressing for amino acids, such as glutamic acid, which is a representative of “umami” equivalent to nucleic acid.
Glutamic acid has been in widespread use for a long time in the form of sodium glutamate as a chemical seasoning or the like. Recently, preference has been shown for the utilization of a culture or extract or the like, which is obtained by culturing yeast naturally containing glutamic acid, in a food or drink.
For example, PTL (Patent Literature) 1 describes a sweetness improver containing a yeast extract as an active component, wherein the yeast extract contains sodium 5′-inosinate and/or sodium 5′-adenylate, sodium 5′-guanylate, sodium 5′-uridylate and sodium 5′-cytidylate at a concentration of 1% to 15%, respectively, and sodium glutamate at a concentration of 1% to 20%.
PTL 2 describes a method for producing a yeast extract containing at least 3% of intracellular free glutamine-derived glutamic acid relative to the extract solids, which includes a step of digesting a yeast containing 15 mg or more of free glutamine per 1 g of dried biomass.
PTL 3 describes a yeast extract obtained by digestion or decomposition of a yeast, wherein when the yeast extract is allowed to pass through a filter membrane having a diameter of 1 μm and the permeate is subjected to gel filtration, and when peptides in the fractionated effluent are detected by absorption spectrophotometry at 220 nm, a portion of peptides having a molecular weight of 10,000 or higher is 10% or higher based on the total amount of all the detected peptides.
PTL 4 describes a yeast extract with a high glutamic acid content, which contains 13% by weight or more of L-glutamic acid (as a Na salt).
PTL 5 describes a yeast extract wherein the content of free amino acid is 25% by weight or more, and the total content of nucleic acid-based gustatory components is 2% by weight or more.
PTL 6 describes a seasoning composition containing nucleic acid-based gustatory substances, glutamic acids, potassium and lactic acid, sodium lactate or potassium lactate, wherein a molar ratio of nucleic acid-based gustatory substance:glutamic acid is in the range of 1:2 to 40, and a molar ratio of (nucleic acid-based gustatory substances+glutamic acids):potassium:(lactic acid, sodium lactate or potassium lactate) is in the range of 1:5 to 80:10 to 80.
PTL 7 describes a yeast which is resistant to a glutamic acid antagonistic growth inhibitor and accumulates glutamic acid in biomass.
PTL 8 describes a method for producing a yeast extract, which uses Yarrowia lipolytica, a yeast having resistance to Nystatin, a drug which obstructs the structure and function of the cell membrane, and which has a capacity to accumulate 530 mg/L or more of L-glutamic acid in biomass.